(a) Field of the Invention
The present invention relates to a method and apparatus for detecting forward/reverse speeds in a continuously variable transmission, and more particularly, to such a method that determines whether a vehicle is in a forward speed state or in a reverse speed state using a speed detector.
(b) Description of the Related Art
Generally, speed ratios of an automatic transmission or a manual transmission are fixed to constant values, and speed ratios are controlled according to a driving condition. However, a continuously variable transmission (CVT) enables speed ratios to be continuously changed within a predetermined range. Ride comfort and acceleration performance are excellent and fuel consumption is low according to a CVT since shifting is achieved only by operating an acceleration pedal. In addition, a CVT may reduce production cost since a CVT has fewer components, compared with an automatic transmission.
When a vehicle provided with a CVT starts moving uphill, the vehicle moves backward slightly. If a transmission control unit does not detect a backward movement of the vehicle when starting and control a start-up of the vehicle, shift shock may occur. Therefore, a transmission control unit must determine whether a vehicle with a CVT is in a forward speed state or in a reverse speed state and control a start-up of the vehicle in accordance with the moving direction of the vehicle in order to reduce shift shock of the vehicle in a case that the vehicle starts moving uphill.
A conventional CVT uses two speed detectors and therefore, production cost can be high. In addition, the structure of the transmission may be complex since a transmission control unit (TCU) receives signals from two speed detectors and controls the transmission by executing a predetermined program. In addition, it is hard to select positions where the two speed detectors may be mounted, and accordingly, the transmission may be large so as to mount the two speed detectors.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.